One of the methods for generating bipartite entanglement is the
entanglement of assistance that is defined in Refs. [1]}, [2]}.
It quantifies the entanglement which could be created by reducing a
multipartite entangled state to an entangled state with fewer
parties (e.g. bipartite) via measurements. Such producing of
entanglement, also called “assisted entanglement", is a special
case of the localizable entanglement [3]},
which is especially important for quantum communication, where
quantum repeaters are needed to establish bipartite entanglement
over a long length scale [4]}. For a pure \(2\otimes 2\otimes n\) 
state, the analytical formula of entanglement of assistance has been
derived by Laustsen et al. [5]}, whereas the
calculation of entanglement of assistance is not easy for a general
pure tripartite state [6]}.
